I'm a science journalist and author of "Distant Wanderers: the Search for Planets Beyond the Solar System" who writes about over-the-horizon technology, primarily astronomy and space science. I’m a former Hong Kong bureau chief for Aviation Week & Space Technology magazine and former Paris-based technology correspondent for the Financial Times newspaper who has reported from six continents. A 1998 winner in the Royal Aeronautical Society's Aerospace Journalist of the Year Awards (AJOYA), I’ve interviewed Nobel Prize winners and written about everything from potato blight to dark energy. Previously, I was a film and arts correspondent in New York and Europe, primarily for newspaper outlets like the International Herald Tribune, the Boston Globe and Canada's Globe & Mail. Recently, I've contributed to Scientific American.com, Nature News, Physics World, and Yale Environment 360.com. I'm a current contributor to Astronomy and Sky & Telescope and a correspondent for Renewable Energy World. Twitter @bdorminey

The European Space Agency’s (ESA) Venus Express orbiter has spent the last eight years trying to dissect its hellish atmosphere and surface. But now with dwindling fuel, by year’s end the spacecraft is expected to make its final plunge into Venus’ toxic atmosphere.

Scale representations of Venus and the Earth shown next to each other. Venus is only slightly smaller. (Photo credit: Wikipedia)

While Venus Express has made scientific progress, planetary scientists say, a few major puzzles have yet to be solved.

Larry Esposito, a planetary scientist at the University of Colorado at Boulder, says the most puzzling things are: How did Venus go bad? How did the high-wind dynamics of the atmosphere arise on Venus? What is its surface made of? And does Venus still have volcanic activity?

Venus Express took infrared images of the planet’s surface and found that its biggest volcanoes do indeed indicate lava flow there within the last 250,000 years.

“Venus Express also detected a sudden increase in sulfur dioxide; the same thing that comes out of unscrubbed coal-powered plants on earth,” said Esposito. “But on Venus Express, it was interpreted as a possible real-time volcanic eruption.”

One explanation is that Venus undergoes giant volcanic eruptions every few decades. But how do these putative eruptions contribute to Venus’ ongoing dense, noxious atmosphere?

Calculations of surface-atmosphere interactions indicate that the planet’s atmospheric sulfur should be “sopped up” by the surface in a few tens of millions of years, says Kevin Baines, a planetary scientist at NASA JPL and the University of Wisconsin at Madison. Baines says this means if the present cloudy atmosphere is typical and ongoing, then there must be active volcanism to resupply the atmosphere with sulfur. He notes that “a hot atmosphere” may “soften” the surface, allowing increased sulfur emission.

One of a handful of potential Venus mission proposals — each vying for a slot in NASA’s Discovery-class mission program — could help clear up Venus’ remaining mysteries.

A proposed VASE (Venus Atmosphere and Surface Explorer) mission might skim the clouds and on a final landing even get data from the surface, says Mark Bullock, a planetary scientist at the Southwest Research Institute in Boulder, and a VASE definition team member.

But Bullock says “if you really want to understand this you have to put lots of balloons in the atmosphere to understand how the surface and the atmosphere interact.”

As for why Venus ultimately became so inhospitable?

The short answer is that as the Sun increases in luminosity, the inner edge of our solar system’s habitable zone also continually moves outward; thus, long ago, Venus simply became too hot to hold onto its liquid water.

Post Your Comment

Post Your Reply

Forbes writers have the ability to call out member comments they find particularly interesting. Called-out comments are highlighted across the Forbes network. You'll be notified if your comment is called out.